Performance improvements such as: better data reliability for user profiles, architectural improvements to speed up page rendering, over 330 memory leak fixes, a new XPCOM cycle collector to reduce entire classes of leaks, and reductions in the memory footprint.

I've never written a big piece of software, so maybe this is an unreasonable question to ask, but how did 330 memory leaks get into Firefox in the first place? The Fox is definitely my preferred browser but it's piss poor performance has been bugging the shit out of me lately, and I have been considering using it only for development and using something else for day-to-day browsing. Performance boosts more than welcome.